The loading of filled lettuce cartons onto a transport vehicle, such as a truck-trailer or railroad freight car, gives rise to a common stacking problem primarily caused by the bulging tops and bottoms of the cartons. After the lettuce is harvested in the field, the lettuce heads are packaged into the cartons for subsequent processing through a cooling plant to maintain the lettuce heads at a sufficiently cool temperature to prevent decay thereof. The cartons are stacked onto pallets which are deposited in a loading and dock area for subsequent loading onto the transport vehicle.
U.S. Pat. No. 4,439,093, for example, discloses a conventional carton handling system for loading the lettuce cartons onto a truck-trailer in a loading and dock area. In particular, the system includes a straight line conveyor for moving the pallets and stacked cartons to a rotator apparatus which functions to receive a pair of pallets and stacked cartons and rotate them through ninety degrees while simultaneously squeezing the cartons. Thereafter, the forks of a standard lift truck are engaged under the stacked cartons to carry the cartons to the truck-trailer and a pallet removing apparatus functions to remove the empty pallets from the rotator apparatus.
Conventional systems of this type give rise to carton damage, spillage and related problems. In addition, a workman may be required for the purpose of holding and/or reloading the cartons on the forks of the lift truck when the lift truck carries the cartons from the rotator apparatus to the truck-trailer. The loading cycle is also prone to delays in that occasional pallet jam-ups and damage to the pallets and cartons may occur in the rotator and pallet removing apparatus.
Further, a substantially large loading area is required to accommodate the rather bulky and stationary rotator apparatus, conveyor and pallet removing apparatus which thus limits the number of companies enabled to use this type of conventional loading system. The complexity of the rotator apparatus and associated pallet removing apparatus also necessitates constant servicing and specially designed high voltage electrical hookups. In addition, seasonal moves of such apparatus to various locations requires that the apparatus be disassembled, shipped to its new location and reassembled, which gives rise to high labor and related costs.
U.S. Pat. Nos. 2,792,133; 2,822,933; 3,123,232; 3,190,461; 3,788,496; 4,037,734; and 4,051,958 disclose other types of conventional carton loading, stacking and related systems and apparatus that also give rise to one or more of the above-discussed prior art problems.